This application claims the priority of Korean Patent Application No. 10-2005-0092159, filed on Sep. 30, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method of determining a similarity between a target image and a reference image, and more particularly, to a method of determining a similarity between a target image and a reference image using a vision system included in a part mounter.
2. Description of the Related Art
A conventional part recognition method used by a part mounter is disclosed in Japanese Patent Publication No. 2002-222420 (title: Image Recognition Method). In this conventional part recognition method, picked-up parts are recognized using geometrical information such as lead shapes or edge shapes of the picked-up parts.
Another conventional part recognition method is disclosed in Japanese Patent Publication No. 2003-256809 (title: Image Processing Apparatus and Method). In this conventional part recognition method, picked-up parts are recognized using brightness information thereof.
According to such conventional part recognition methods, a part mounter can recognize parts with characteristic shapes but cannot recognize parts without characteristic shapes. FIG. 1 illustrates parts with characteristic shapes. FIG. 2 illustrates parts without characteristic shapes.
To recognize the parts without characteristic shapes as illustrated in FIG. 2, reference images, which are which are images of portions of reference parts of each type, are stored. Then, whether an image of a picked-up part includes a reference image is determined. In so doing, the type of the picked-up part can be determined.
In other words, it is required to determine a similarity between a target image, which is an image of part of a picked-up image, and a reference image. Therefore, a method of accurately determining a similarity between a target image and a reference image, even though the original pixel-values of pixels of the target image minutely vary according to photographing and image-processing conditions, is required.